1. Field of the Invention
This invention relates to reshaping articles from certain scrap copolymer. More specifically, the invention relates to a process for preparing a solution from which articles of a copolymer consisting essentially of recurring units of the formulas ##STR1## A MOLE RATIO OF FROM 95:5 TO 20:80, RESPECTIVELY, WHEREIN Ar is a divalent aromatic radical and R is a C.sub.1 to C.sub.4 alkyl, can be shaped. The process involves degrading scrap said copolymer in oleum and, heating the resulting solution to form in solution a copolymer consisting essentially of recurring units of the formulas ##STR2## A MOLE RATIO OF FROM 95:5 TO 20:80, RESPECTIVELY, WHEREIN Ar and R have the same meaning as defined above. As used herein the term "Copolymer A" refers to the above copolymer consisting essentially of units (a) and (a') and "Copolymer B" refers to the above copolymer consisting essentially of units (b) and (b'). Articles may be shaped from the resulting polymer solution by combining the solution with an aqueous medium (e.g. water or aqueous sulfuric acid) whereby Copolymer B hydrolyzes to yield Copolymer A which coagulates in the aqueous medium.
2. Prior Art
Initially, Copolymer A is prepared by a solution technique in which certain monomers, for example, terephthalic acid, dimethylterephthalate and hydrazine sulfate are reacted in oleum to yield a sulfuric acid solution of Copolymer B. This solution (or dope) is then used to shape articles, such as fibers, by combining the solution with an aqueous medium, for example, water or dilute sulfuric acid whereby Copolymer B hydrolyzes to yield Copolymer A which coagulates in the aqueous medium. Coupled processes for preparing fibers of Copolymer A are described in British Pat. Nos. 1,407,439 and 1,417,568 and U.S. Pat. No. 3,644,297 and in commonly assigned U.S. application Ser. No. 520,503.
When producing shaped articles of Copolymer A, as with most processes for producing shaped articles of polymers, a certain amount of scrap Copolymer A is generated either in the form of rejected articles or waste polymer. Techniques which have been developed in the past for reshaping articles from scrap polymer depend on the polymer being shaped by melt extrusion techniques and/or being soluble in a suitable solvent from which articles can be obtained by solution techniques. Unfortunately, Copolymer A on the one hand cannot be shaped by melt extrusion techniques due to its high melting point and on the other hand it is insoluble in most organic solvents and degrades in sulfuric acid. While Copolymer A will dissolve in hexafluoroisopropanol, this solvent is too costly to be seriously considered as a suitable solvent for large scale operations. Thus, techniques which have been used in the past for reshaping articles from scrap polymer are not suitable for use with scrap Copolymer A.
It is therefore an object of the present invention to provide a process for reshaping articles from scrap Copolymer A.
More specifically, it is an object of the present invention to provide a process for utilizing scrap Copolymer A for preparing a solution from which useful articles of Copolymer A can be shaped.